Although continuous type dampeners have been known and used successfully for quite some time, their use has been limited primarily to sheet and web fed offset commercial type printing presses which operate at relatively low speeds and which print on specially coated offset paper stock. Attempts to employ these dampening mechanisms on high speed web offset newspaper presses, however, have been for the most part unsuccessful. The lack of success is due primarily to the inability of the conventional transfer roller, which has a smooth, continuous, highly polished surface, to feed sufficient water to the plate at high press speeds to compensate for the highly absorbent nature of newsprint paper.
Merely increasing the surface speeds and/or varying the slip ratios of the coacting dampening rollers proved not to be the solution. Such changes tended to create excessive turbulence of the fluid in the fountain and the dampening function became progressively more erratic and inconsistent as the press speeds approached the upper, normal operating ranges. For the most part, therefore, it has been necessary to operate such presses below their rated speeds or to use ductor or brush type dampeners.